Method and device for communicating true runway braking performance using data from the flight data management systems of landed aircraft

ABSTRACT

A method and apparatus for calculating a standardized value for the actual runway braking coefficient of friction of one or more arriving aircraft using data from each aircraft&#39;s flight data recorder or flight data management system, standardizing the calculated information to provide redundancy and to make it usable by subsequently arriving aircraft, and reporting the calculated standardized value information to individuals and agencies including air traffic control, airport operations and maintenance, and aircraft pilots and ground crews; and A method and apparatus for calculating the actual runway braking coefficient of friction of an aircraft using data from the aircraft&#39;s flight data recorder or flight data management system, transmitting the data in real-time to an off-aircraft high-power computing system, calculating off-aircraft the landing aircraft&#39;s actual runway braking coefficient of friction, and reporting the calculated information to individuals and agencies including air traffic control, airport operations and maintenance, and aircraft pilots and ground crews.

This application is a continuation of co-pending U.S. application Ser.No. 12/661,657, filed Mar. 20, 2010, which, in turn, is acontinuation-in-part of U.S. application Ser. No. 11/352,984, filed Feb.13, 2006, now U.S. Pat. No. 7,797,095, issued Sep. 14, 2010, which, inturn, claims the benefit of and priority from U.S. Provisionalapplication No. 60/654,914, filed Feb. 23, 2005, now expired, all of thedisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of invention

This invention relates to the method and the device of calculatingaircraft braking friction and other aircraft performance and pavementsurface characteristics parameters related to aircraft landing andtakeoff including but not limited to aircraft braking action, aircrafttakeoff distance, aircraft landing distance, runway surface conditionsand runway surface friction—from now on referred as true aircraftlanding performance parameters—based on the data collected or otherwiseavailable on board of an aircraft in electronic or other format from theaircraft Flight Data Recorder (FDR) or any other flight data providingor management system for example the Quick Access Recorder (QAR). Ingreater particularity, this invention relates to a method and apparatusfor the determination of a standardized or normalized coefficient ofbraking friction using data from the flight data management systems(FDMS) and flight data recorders (FDRs) of individual arriving aircrafton a particular airport runway, thereby creating a data set which isboth redundant and continuously updated, and reporting this informationin real-time to individuals and agencies including air traffic control,airport operations and maintenance, and aircraft pilots and groundcrews.

2. Background

Under severe winter conditions airlines, airports, civil aviationorganizations and countries rigorously impose limits on aircrafttakeoff, landing and other surface movement operations as well asenforce weight penalties for aircraft takeoffs and landings. Theselimits depend on the weather, runway and taxiway surface conditions andaircraft braking and takeoff performance. At the present these limitsare calculated from the assumed aircraft braking performance based onrunway conditions. These conditions are established by visualinspections, weather reports and the measurements of runway frictioncoefficient using ground friction measurement equipment.

At the present time, there are several practices to calculate theassumed aircraft braking performance:

1. The Canadian CRFI Method:

The CRFI method comprises of a runway surface friction measurementperformed by braking a passenger vehicle traveling on the runway at acertain speed and measuring the maximum deceleration of it at severallocations along the length of the runway. The measured deceleration datais taken then and a braking index chart is used to calculate the assumedaircraft braking performance. The obtained aircraft landing performancedata and calculated assumed braking friction is provided to airlineoperators, pilots and airport personnel for decision making.

2. The reported runway friction coefficient by a runway frictionmeasurement equipment:

There are a great many number of runway friction measurement devicesmanufactured by different companies, in different countries and workingbased on different principles. Some of the most common devices are: (a)continuous friction measurement equipment (CFME); (b) decelerometers;and (c) side force friction coefficient measurement equipment. Thisequipment is operated by airport operation personnel according to themanufacturer's instructions on the runways, aprons, and taxiways and themeasured friction coefficient is recorded. The recorded frictioncoefficient is then distributed to airline operation personnel, pilots,and airport personnel. The measured coefficient of friction is dependentof the measurement device, under the same conditions and on the samerunway different runway friction measurement devices based on differentprinciples will record different runway friction coefficients. Theserunway friction coefficients are assumed to relate to actual aircraftlanding and takeoff performance.

3. The new proposed IRFI method:

The International Runway Friction Index (IRFI) is a computational methodto harmonize the reported runway friction numbers reported by the manydifferent runway surface friction measurement equipments. The method wasdeveloped through an international effort with 14 participatingcountries. The method is a mathematical procedure based on simple linearcorrelations. The IRFI procedure is using a mathematical transformationto take the reported measurement of a runway friction measurement deviceand compute using simple mathematical methods an index called the IRFI.The mathematical procedures are the same for all the different runwayfriction measurement device using a different set of constant parametersthat was determined for each individual device. It is assumed that usingthis procedure the different runway friction measurement devicesreporting different friction coefficients can be harmonized. Thecalculated IRFI is assumed to correlate to aircraft landing and takeoffperformance.

4. Pre-determined friction levels based on observed runway conditions,current and forecasted weather conditions:

This method is available for airport operators according to newregulations. The method is based on airport personnel driving throughthe runway and personally observing the runway surface conditions. Theice, snow, water and other possible surface contaminants are visuallyobserved and their depth measured or estimated by visual observation.The estimated runway conditions with weather information are then usedto lookup runway friction coefficient in a table.

All these above mentioned practices are based on the measurement of therunway friction coefficient using ground friction measuring equipment,visual observation, weather information or combinations of these.However, according to present practices, there are several problems withthe measurement of the runway friction coefficient using these methods.

1. Need of a special device/car: there is a special car needed to beable to measure the runway friction coefficient. There are specialdevices to measure the runway friction coefficient that are commerciallyavailable; however, most of these devices are very expensive. Therefore,not every airport can afford to have one.

2. Close of runway: for the duration of the measurement the runway hasto be closed for takeoffs and landings as well as any aircraft movement.The measurement of the runway surface friction takes a relatively largeamount of time since a measuring device has to travel the whole lengthof the runway at a minimum one time but during severe weather conditionsit is possible that more than one measurement run is needed to determinerunway surface friction. The closing of an active runway causes thesuspension of takeoff and landing aircraft operations for a lengthenedperiod of time and therefore is very costly for both the airlines andthe airport. The using of ground vehicles to measure runway frictionposes safety hazard especially under severe weather conditions.

3. Inaccurate result due to lack of maintenance and inaccuratecalibration level: the result of the measurements are very dependent ofthe maintenance and the calibration level of measurement devices,therefore the result can vary much, and could lose reliability.

4. Confusing results due to the differences between ground frictiondevices: It has been established that the frictional values reported bydifferent types of ground friction measurement equipment aresubstantially different. In fact, the same type and manufacture, andeven the same model of equipment frequently report highly scatteredfrictional data. Calibration and measurement procedures are differentfor different types of devices. The repeatability and reproducibilityscatter, or in other words uncertainty, of measurements for each type ofground friction measurement device is therefore amplified and the spreadof friction measurement values among different equipment types issignificant.

5. Inaccurate result due to rapid weather change: Airport operationpersonnel, in taking on the responsibility of conducting frictionmeasurements during winter storms, find it difficult to keep up with therapid changes in the weather. During winter storms runway surfaceconditions can change very quickly and therefore friction measurementresults can become obsolete in a short amount of time, thusmisrepresenting landing and takeoff conditions.

6. Inaccurate result due to the difference between aircraft and theground equipment: It is proven that the aircraft braking frictioncoefficients of contaminated runways are different for aircraftscompared to those reported by the ground friction measurement equipment.

7. Inaccurate result due to the lack of uniform runway reportingpractices: For many years the international aviation community has hadno uniform runway friction reporting practices. The equipment used andprocedures followed in taking friction measurements varies from countryto country. Therefore, friction readings at various airports because ofdifferences in reporting practices may not be reliable enough tocalculate aircraft braking performance.

Therefore this invention recognizes the need for a system directlycapable of determining the true aircraft landing performance parametersbased on the data collected by and available in the aircraft Flight DataRecorder (FDR) or other flight data management systems. By utilizing thenovel method in this invention for the first time every involvedpersonnel in the ground operations of an airport and airline operationsincluding but not limited to aircraft pilots, airline operation officersand airline managers as well as airport operators, managers andmaintenance crews, will have the most accurate and most recentinformation on runway surface friction and aircraft braking action,especially on winter contaminated and slippery runways.

Utilizing this method the aviation industry no longer has to rely ondifferent friction reading from different instrumentations and fromdifferent procedures.

Therefore, this method will represent a direct and substantial benefitfor the aviation industry.

BRIEF SUMMARY OF THE INVENTION Objective of the Invention

The objective of this invention is to provide every personnel involvedin the ground operations of an airport and involved in airlineoperations including but not limited to aircraft pilots, airlineoperation officers, and airline managers, as well as airport operators,managers and maintenance crews, the most accurate and most recentinformation on the true aircraft landing and takeoff performanceparameters to help in a better and more accurate safety and economicaldecision making, and to prevent any accident, therefore save lives.

BRIEF SUMMARY OF THE INVENTION

This unique and novel invention is based on the fact that most modernairplanes throughout the entire flight including the takeoff and landingmeasures, collect and store data on all substantial aircraft systemsincluding the braking hydraulics, speeds and hundreds of otherperformance parameters. During the landing maneuver real time, or afterthe aircraft is parked at the gate, this data can be retrieved,processed and the true aircraft landing performance parameters can becalculated.

During a landing usually an aircraft uses its speed brakes, spoilers,flaps and hydraulic and mechanic braking system and other means todecelerate the aircraft to acceptable ground taxi speed. The performanceof these systems together with many physical parameters including butnot limited to various speeds, deceleration, temperatures, pressures,winds and other physical parameters are monitored, measured, collectedand stored in a data management system on board of the aircraft (FIG.1).

All monitored parameters can be fed real time into a high poweredcomputer system, either on-board the aircraft or in a fixed remotelocation, that is capable of processing the data and calculating allrelevant physical processes involved in the aircraft landing maneuver.Based upon the calculated physical processes the actual effectivebraking friction coefficient of the landing aircraft can be calculated.This, together with other parameters and weather data, can be used tocalculate the true aircraft landing performance parameters (FIG. 6).

If real time data processing is not chosen, then the collected data fromthe aircraft can be transported by wired, wireless or any other meansinto a central processing unit where the same calculation can beperformed (FIG. 8).

The obtained true aircraft landing performance parameters data then canbe distributed to every involved personnel in the ground operations ofan airport and airline operations including but not limited to aircraftpilots, airline operation officers, and airline managers, as well asairport operators, managers and maintenance crews.

Utilizing the novel method in this invention for the first time everypersonnel involved in the ground operations of an airport and airlineoperations including but not limited to aircraft pilots, airlineoperation officers, and airline managers, as well as airport operators,managers and maintenance crews, will have the most accurate and mostrecent information on runway surface friction and aircraft brakingaction.

Utilizing this method, all the above mentioned (see BACKGROUND OF THEINVENTION) problems can be solved:

1. No need of a special device/car: this method uses the airplane itselfas measuring equipment, therefore no additional equipment is needed.Moreover, no additional sensor is needed. This method uses the readingsof present sensors and other readily available data of an aircraft.

2. No need for closing of runway: the duration of the measurement is thelanding of the aircraft itself. Therefore the runway does not have to beclosed.

3. No inaccurate result due to maintenance and the calibration level:because this method uses the aircraft itself as the measuring device,there is no variation due to the maintenance and the calibration levelof these ground friction measuring devices. The result of thecalculation will give back the exact aircraft braking friction theaircraft actually develops and encounters.

4. No inaccurate result due to the different between ground frictiondevices: because this method uses the aircraft itself as the measuringdevice, there is no variation due to the different ground frictionmeasuring devices.

5. Accurate result even in rapid weather change: As long as aircraft arelanding on the runway, the most accurate and most recent information onthe true aircraft landing performance parameters will be provided byeach landing.

6. No inaccurate result due to the difference between aircraft and theground equipment: because this method uses the aircraft itself as themeasuring device, there is no discrepancy in the measured and realfriction due to the difference between aircraft and the groundequipment.

7. No inaccurate result due to the lack of uniform runway reportingpractices: because this method uses the aircraft itself as the measuringdevice, there is no variation due to the difference in reportingpractices.

Utilizing this method the aviation industry no longer has to rely ondifferent friction readings from different instrumentations and fromdifferent procedures.

Therefore, this method represents a direct and substantial safety andeconomic benefits for the aviation industry.

The significance of this invention involves saving substantial amountsof money for the airline industry by preventing over usage of criticalparts, components of the aircraft including but not limited to brakes,hydraulics, and engines.

While increasing the safety level of the takeoffs, it could generatesubstantial revenue for airlines by calculating the allowable take offweight, thus permissible cargo much more precisely.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 Flight Data Recorder schematic: It is an illustration for thedata collection structure of the Flight Data Recorder (FDR).

FIG. 2 Example Pressure Altitude (ft) versus Time(s) data from theFlight Data Recorder Data: It is a graphical illustration of the datafrom the FDR, which shows an example for the Pressure Altitude (ft)versus Time(s) during a landing.

FIG. 3 Example Brake Pressure (psi) versus Time(s) data from the FlightData Recorder Data: It is a graphical illustration of the data from theFDR, which shows an example the Brake Pressure versus Time(s) during alanding.

FIG. 4 Example AutoBrake setting versus Time(s) data from the FlightData Recorder Data: It is a graphical illustration of the data from theFDR, which shows an example the AutoBrake settings versus Time(s) duringa landing.

FIG. 5 A fraction of example data from the Flight Data Recorder: It isan illustration of the data from the FDR.

FIG. 6 The method of the calculation: The flow chart of the calculationsand computations of the method.

FIG. 7 An example for a friction limited braking: A graphicalpresentation of an example for a friction limited braking.

FIG. 8 Post processing and distribution: It is an illustration of theschematic of the post processing and distribution.

FIG. 9 Real-time processing and distribution: It is an illustration ofthe schematic of the real-time processing and distribution.

FIG. 10 A schematic flow chart illustrating a further embodiment of theinvention in which a summary or normalized value of runway brakingperformance is created from the true aircraft landing parametersdetermined using the method of FIG. 6 based on a sequence of two or morelanding aircraft.

FIG. 11 A schematic flow chart illustrating a further embodiment of theinvention incorporating real-time off-aircraft processing anddistribution.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1—This unique and novel invention is based on the fact that everyairplane during landing uses the hydraulics and braking system. During alanding usually an aircraft uses its speed brakes, spoilers, flaps andhydraulic and mechanical braking system and other means to deceleratethe aircraft to acceptable ground taxi speed. The relationship of thesesystems to the deceleration of an aircraft in optimal conditions is aknown quantity. Therefore any deviation from optimal deceleration isnecessarily due to non-optimal weather and runway surface conditions.The performance of these systems together with many physical parametersincluding but not limited to various speeds, deceleration, temperatures,pressures, winds and other physical parameters are monitored, measured,collected and stored in a data management system on board of theaircraft. This figure presents the schematics of the three majorcomponents of data sources onboard of an aircraft relevant to thisinvention, the measured and recorded parameters related to the brakingsystem, the measured and recorded parameters relating to the engines,flight and other control systems of the aircraft, and the dynamic,external and environmental parameters measured and recorded.

FIG. 2—FIG. 5. This invention uses the sequence of data points recordedfrom the touch down of the aircraft until it reaches the normal taxiingspeed or comes to a stop. In the continuous data stream of the flightdata management system the touch down is marked by several events makingit possible to detect the beginning data point of the calculationprocess. From that point until the aircraft comes to complete stop atthe gate every necessary data point can be identified within therecorded data, with a preferred sampling frequency of at least one datasample per second. FIG. 2 shows the recorded altitude measurements foran actual landing FIG. 3 depicts the measured the recorded hydraulicbraking pressures, FIG. 4 presents the recorded data for the auto-brakeselection and FIG. 5 illustrate the format of the recorded data that canbe obtained form a digital flight data management system.

FIG. 6—To arrive to the end result a number of different mathematicaland physical modeling approaches are possible through different sets ofdynamic equations and/or various methods of simulations based upon theavailability of different sets of data from the flight data managementsystem.

The following equations only represent an example of the possibleapproaches, and therefore the invention and the presented method is notlimited to these equations.

6.1—The following data is used as one of the possible minimum data setsfor the calculation, although more and/or different data can be utilizedto calculate the same parameters and/or improve the precision of thecalculation.

Data from the Flight Data Recorder: V_(air)—Air Speed, P_(LB),P_(RB)—Left and Right Brake Pressure, V_(ground)—Ground Speed,A_(x)—Longitudinal Acceleration, A_(c)—Vertical Acceleration,E_(RPM)—Engine RPM, S_(spoiler)—Spoiler setting, S_(airbrake)—Airbrakesetting, S_(aileron)—Aileron setting, C_(flap)—Flap configuration,θpitch—Pitch, S_(RT)—Reverse thrust setting, S_(T)—Engine thrustsetting.

The following environmental data are used in the calculation.T_(air)—Air Temp, P_(alt)—Pressure Altitude, P_(air)—Air Pressure,H_(%)—Relative humidity, Δ_(Runway)—Runway elevation.

The following aircraft parameters are used in the calculation.M_(landing)—Landing Mass, E_(type)—Engine type, N_(engine)—Number ofengines, TY_(tire)—Tire type, TY_(aircraft)—Aircraft type.

6.2—The method calculates, through a three-dimensional dynamic model,all relevant physical processes involved in the aircraft landingmaneuver and separates them so they are individually available for use.The first intermediate result of the method is the time or distancehistory of all relevant, separated, interdependent decelerationsgenerated by the different systems in an aircraft. These decelerationsare cumulatively measured by the onboard measurement system and reportedin the flight data stream. The separated decelerations calculated fromthe different physical processes make it possible to calculate the truedeceleration developed only by the actual effective braking frictioncoefficient of the landing aircraft.

Based on the above, the software calculates the brake effectiveacceleration vs. time based on Equation (1).A _(Be) =A _(x) −A _(Drag) −A _(ReverseThrust) −A _(Rolling Resistance)−A _(Pitch)  (1)

where A_(Be) is the brake effective acceleration;

A_(x) is the measured cumulative longitudinal acceleration (6.1);

A_(Drag) is the deceleration due to the aerodynamic drag,A _(Drag) =f(V _(air) ,S _(spoiler) ,S _(airbrake) ,S _(aileron) ,C_(flap) ,T _(air) ,P _(air) ,H _(%) ,M _(landing) ,TY _(aircraft))  (2)

where V_(air), S_(spoiler), S_(airbrake), S_(aileron), C_(flap),T_(air), P_(air), M_(landing), TY_(aircraft), are parameters from 6.1;

A_(ReverseThrust) is the acceleration caused by thrust/reverse-thrust,A _(ReverseThrust) =f(E _(type) ,N _(engine) ,T _(air) ,P _(air) ,H _(%),E _(RPM) ,S _(RT) ,M _(landing) ,TY _(aircraft))  (3)

where E_(type), N_(engine), T_(air), P_(air), H_(%), E_(RPM), S_(RT),M_(landing); TY_(aircraft), are parameters from 6.1;

A_(RollingResistance) is the cumulative deceleration due to othereffects such as tire rolling resistance, runway longitudinal elevation,A _(Rolling Resistance) =f(TY _(tire) ,V _(g) ,M _(landing))  (4)

where TY_(tire), V_(g), M_(landing) are parameters from 6.1;

A_(pitch) is due to the runway elevationA _(pitch) =f(Δ_(Runway))  (5)

where Δ_(Runway) is the runway elevation from 6.1.

This true deceleration (A_(Be)) developed only by the actual effectivebraking friction coefficient of the landing aircraft, then can be usedin further calculations to determine the true aircraft brakingcoefficient of friction.

In practicing the invention, a suitable way of calculating A_(Drag) is:A _(Drag)=½·((C _(D)·ρ)/M _(landing))·V _(TAir) ² ·S(S _(spoiler) ,S_(airbrake) ,S _(aileron) ,C _(flap) ,TY _(aircraft))

where:

C_(D) is coefficient of aerodynamic drag, constant parameter

ρ is the air density;

V_(TAir) is the True Airspeed of the aircraft;

S_(Spoiler) is active surface area of spoilers;

S_(AirBrakes) is active surface area of air brakes;

S_(aileron) is active surface area of ailerons; and

S_(flap) is active surface area of flaps.

A suitable way of calculating A_(Reverse) is:A _(Reverse)=(MaxEngineThrust/M _(landing))·η_(reverser) ·N _(engine) ·C_(EngineType)(1+E ^((k/Nengine)·(VTAir+b)))

where:

MaxEngineThrust is the maximum available thrust of a the engines;

M_(landing) is the aircraft mass during landing;

η_(reverser) is the efficiency of the thrust reverser;

N_(engine) is the rotational speed of the low pressure rotor of theengine;

C_(EngineType) is a constant depending on jet engine type;

k is a constant turbofan engine speed parameter depending on jet enginetype;

V_(TAir) is the True Airspeed of the aircraft; and

b is a constant engine speed parameter depending on engine type.

A suitable way of calculating A_(RollingResistance) is:A _(RollingResistance)=Const_(1,TireType) ·V ^(2.5)_(Ground)+Const_(2,TireType)

where:

Const_(1,TireType) is a constant value dependent on tire type,construction and material;

V_(Ground) is the aircraft ground speed; and

Const_(2,TireType) is a constant value dependent on tire type,construction and material.

A suitable way of calculating Lift is:Lift=((ρ/2)·C _(L)′·square root(C _(D) −C _(1,TYAircraft))/C_(2,TYAircraft))·V _(TAir) ·S(S _(spoiler) ,S _(airbrake) ,S _(aileron),C _(flap) ,TY _(aircraft))

where:

C′_(L) is the aerodynamic list coefficient of the aircraft activesurface;

C_(D) is the coefficient of aerodynamic drag, constant parameter;

C_(1,TYAircraft) is a constant aerodynamic parameter dependent onaircraft type and landing configuration;

C_(2,TYAircraft) is a constant aerodynamic parameter dependent onaircraft type and landing configuration;

V_(TAir) is the True Airspeed of the aircraft;

C_(flap) is a constant added active surface area parameter; and

TY_(Aircraft) type of aircraft.

A suitable way of calculating LoadTransfer is:LoadTransfer=((CG _(height) ·A _(Be) +g·CG_(DistanceFromNoseGear))/WheelBase)·M _(landing)

where:

CG_(height) is the height of the aircraft center of gravity above theground;

g is the natural acceleration of gravity;

CG_(DistanceFromNoseGear) is the distance of the aircraft center ofgravity from the nose gear;

WheelBase is the distance between the nose and landing gears; and

M_(landing) is the aircraft mass during the landing.

6.3—Using the recorded data stream of the aircraft with the parametersindicated in point 6.1, plus weather and environmental factors reportedby the airport or measured onboard of the aircraft and thereforeavailable in the recorded data, together with known performance anddesign parameters of the aircraft available from design documentationand in the literature, the dynamic model calculates all relevant actualforces acting on the aircraft as a function of the true ground and airspeeds, travel distance and time. Using the results, the dynamic wheelloads of all main gears and the nose gear can be calculated.

Since the dynamic vertical acceleration of the aircraft is measured bythe onboard inertial instrumentation, the effective dynamic wheel load(N) can be calculated by the deduction of the calculated retardingforces by means of known aircraft mass; together with the determinedgravitational measurement biases introduced by runway geometry andaircraft physics using Equation 6 through 9.N=M _(landing)·cos(θ_(pitch))·g−Lift-Load Transfer-MomentumLift+g(A _(c),M _(landing))  (6)

where

Lift is the computed force of the sum of all lifting forces acting onthe aircraft through aerodynamics:Lift=f(V _(air) ,S _(spoiler) ,S _(airbrake) ,S _(aileron) ,C _(flap) ,T_(air) ,P _(air) ,H _(%) ,M _(landing) ,TY _(aircraft))

where V_(air), S_(spoiler), S_(airbrake), S_(aileron), C_(flap),T_(air), P_(air), H_(%), M_(landing), TY_(aircraft) are parameters frompoint 6.1;

LoadTransfer is the load transfer from the main landing gear to the nosegear due to the deceleration of the aircraft:LoadTransfer=f(A _(Be) ,M _(landing) ,TY _(aircraft))  (8)

where A_(Be), M_(landing), TY_(aircraft) are parameters from 6.1;

MomentumLift is the generated loading or lifting forces produced bymoments acting on the aircraft body due to the acting points of lift,thrust and reverse-thrust forces on the aircraft geometry:MomentumLift=f(S _(Thrust) ,S _(RT) ,C _(flap) ,TY _(aircraft))  (9)

where S_(Thrust), S_(RT), C_(flap),TY_(aircraft) are parameters frompoint 6.1; and

g(A_(c), M_(landing)) is the dynamic force acting on the landing geardue to the dynamic vertical movement of the aircraft, and thus thevarying load on the main gear due to the runway roughness,

where A_(c), M_(landing) are parameters from point 6.1.

6.4—The deceleration caused by the wheel braking system of the aircraftcalculated in point 6.2 (A_(Be) is the true brake effectivedeceleration), together with the computed actual wheel load forcesacting on the main gears of the aircraft can be used to calculate thetrue braking coefficient of friction. First the actual true decelerationforce or friction force (F_(Fr)) caused by the effective braking of theaircraft have to be computed. From the brake effective deceleration(A_(Be)) obtained in 6.2 and the available aircraft mass, the methodcalculates the true effective friction force based on the formula:F _(Fr) =M _(landing) ·A _(Be)  (10)

where M_(landing) is the landing mass of the aircraft from point 6.1 andA_(Be) is the calculated brake effective deceleration from Equation (1).

The determined true deceleration force (F_(Fr)) in equation 10 togetherwith the actual effective dynamic wheel load (N) obtained in 6.3 can beutilized to calculate the true effective braking coefficient of friction.mu. using equation 11:μ=F _(Fr) /N  (11)

where

N is the calculated effective dynamic wheel force acting on the tire(6.3); and F_(Fr) is the friction force from Equation (10).

6.5—Using the calculated effective true frictional forces, together withparameters measured by the aircraft data management system (such asdownstream hydraulic braking pressure), a logical algorithm based on thephysics of the braking of pneumatic tires with antiskid braking systemswas designed to determine whether the maximum available runway frictionwas reached within the relevant speed ranges of the landing maneuver.

Together with the actual friction force the following logic is used bythis invention to determine:

(A) If friction limited braking is encountered. If the actual availablemaximum braking friction available for the aircraft was reached by thebraking system and even though more retardation was needed the brakingsystem could not generate because of the insufficient amount of runwaysurface friction a friction limited braking was encountered.

(B) If adequate friction for the braking maneuver was available. Iffriction limited braking was not encountered and the braking was limitedby manual braking or the preset level of the auto-brake system, theadequate surface friction and actual friction coefficient can becalculated and verified.

6.6—In order to make sure that the auto-brake and antiskid systems ofthe aircraft were working in their operational range, the algorithm isanalyzing the data to look for the friction limited sections only in anoperational window where the landing speed is between 20 m/s and 60 m/s.

6.7—From the computed true effective braking coefficient of friction μcalculated in 6.4 the method computes the theoretically necessaryhydraulic brake pressure P_(brake) and from the dynamics of the landingparameters an applicable tolerance is calculated t.

6.8—The data is analyzed for the deviation of the applied downstreamhydraulic brake pressure from the calculated theoretical brake pressurefrom 6.7 according to the obtained effective braking friction within theallowed operational window by the determined t tolerance. A sharpdeviation of the achieved and the calculated hydraulic braking pressureis the indication of friction limited braking. When sharply increasedhydraulic pressure is applied by the braking system, while nosignificant friction increase is generated, the potential of truefriction limited braking occurs.

FIG. 7—A graphical presentation for an example for the friction limitedbraking, where it can be seen that that a sharply increasing hydraulicpressure is applied by the braking system, while the friction isdecreasing. This is a very good example for a true friction limitedbraking.

The Different Applications of this Method

The Post-Processing: FIG. 8—One possible approach in obtaining the trueaircraft landing performance parameters is a method of post processing.The data from the aircraft flight data management system is retrievednot real time but only after the aircraft is finished its landing,taxiing and other ground maneuvers and arrived at its final groundposition. The schematic of this approach is described in FIG. 8.

8.1—All monitored and available data is sent to the flight datamanagement system throughout the aircraft landing and ground maneuver.

8.2—Flight Data Management system collects, processes and stores theretrieved data in a data storage. The data storage is in fact part ofthe Flight Data Management system where all the data is stored.

8.3 Data transfer—After the airplane stopped at the gate or otherdesignated final position, the collected data from the aircraft can betransported by wired, wireless or other means into a central processingunit, either on-board or remotely located.

8.4 High Power computer—All recorded parameters transported from theaircraft can be fed into a computer system, either on-board or remote,which is capable of processing the data and calculating/simulating allrelevant physical processes involved in the aircraft landing maneuverand the actual effective braking friction coefficient of the landingaircraft and the true aircraft landing performance parameters can becomputed and made ready for distribution.

8.5 Data Distribution—The computer distributes the calculated truelanding parameters to other interested parties through wired, wirelessor other data transportation means.

Real-Time Data Processing

FIG. 9—In the case of real time data processing, all monitoredparameters can be fed real time into an onboard high power computersystem that is capable of processing the data and calculating allrelevant physical processes involved in the aircraft landing maneuver.Based upon the calculated physical processes the actual effectivebraking friction coefficient of the landing aircraft can be calculated.This together with other parameters and weather data can be used tocalculate the true aircraft landing performance parameters. In case thecalculation finds a true friction limited section, a warning can be sentto the pilot to prevent any accident, such as over run or slide off therunway.

9.1—All monitored and available data is sent to the flight datamanagement system throughout the aircraft landing and ground maneuver.

9.2—Flight Data Management system collects, processes and stores theretrieved data in a data storage. The data storage is in fact part ofthe Flight Data Management system where all the data is stored.

9.3—High power computer system: All monitored parameters fed real timeinto a computer system, either on-board or remote, which is capable ofprocessing the data and calculating/simulating all relevant physicalprocesses involved in the aircraft landing maneuver and the actualeffective braking friction coefficient of the landing aircraft and thetrue aircraft landing performance parameters.

9.4—Pilot warning: Based on the calculated aircraft braking coefficientand the method to search for friction limited braking it gives a warningin case the friction is too low or continuously informs the driver ofthe generated and available braking and cornering coefficient offriction.

9.5—Distribution: The computer distributes the calculated true landingparameters to other interested parties.

Significance of the Invention:

Utilizing the novel method in this invention for the first time allpersonnel involved in the ground operations of an airport as well asairline personnel involved in operations including but not limited toaircraft pilots, airline operation officers and airline managers as wellas airport operators, managers and maintenance crews, will have the mostaccurate and most recent information on runway surface friction andaircraft braking action.

Utilizing this method the aviation industry no longer has to rely ondifferent friction readings from different instrumentations and fromdifferent procedures or assumed friction levels based on visualobservation and weather data.

Therefore, this method represents a direct and substantial safety andeconomic benefits for the aviation industry.

Economic Benefits:

The significance of this invention involves knowing the true aircraftlanding performance parameters for landing which yields substantialfinancial savings for the airline industry. While increasing the safetylevel of the takeoffs, it could also generate substantial revenue forairlines.

Therefore a system directly capable of determining the true aircraftlanding performance parameters would represent direct and substantialeconomic benefit for the aviation industry including but not limited to:

1. Preventing over usage of critical parts, components of the aircraftincluding but not limited to brakes, hydraulics, and engines.

2. The distribution of the calculated parameters for the airportmanagement helps making more accurate, timely and economic decisionsincluding but not limited to decision on closing the airport or decisionon the necessary maintenance.

3. The calculated parameters reported to the airline management yieldsmore accurate and economic decision making including but not limited topermitting the calculation of allowable take off weights much moreprecisely thus increasing the permissible cargo limits.

Safety Benefits:

The significance of this invention involves the precise assessment ofthe true runway surface characteristics and aircraft braking and landingperformance by providing the true aircraft landing performanceparameters. This is fundamental to airport aviation safety, andeconomical operations especially under winter conditions and slipperyrunways. Thus, a system directly capable of determining the trueaircraft landing performance parameters real-time and under anyconditions without restricting ground operations of an airport wouldrepresent direct and substantial safety benefit for the aviationindustry including but not limited to:

1. Providing real-time low friction warning to help pilots to makecritical decisions during landing or take-off operations to preventaccidents, costly damages or loss of human lives.

2. Eliminating the confusion in the interpretation of the differentGround Friction Measuring Device readings and therefore giving precisedata to airport personnel for critical and economical decision making inairport operations and maintenance.

3. Giving an accurate assessment of the actual surface conditions of therunway, that could be used in the aircraft cargo's loading decisionmaking for safer landing or take-offs.

4. Providing accurate data for distribution to airport managementpersonnel assisting them in more accurate, timely and safe decisionmaking.

5. Providing data to be reported to pilots about to land for safer andmore accurate landing preparation.

6. Providing data to be reported to pilots about to take off for saferand more accurate takeoff preparation

7. It could be reported to the airline management to for more accuratesafety decision making.

Normalized Summary Braking Values. According to another aspect of theinvention, best understood by reference to the flow diagram of FIG. 10,true aircraft runway coefficients of friction parameters calculated fromtwo or more sequential landings are used to create and report a singleoverall “standardized” or “normalized” summary value, similar to aweighted average, thus adding redundancy and reliability to theresulting information.

Normalization is a well-known a mathematical operation in which diversedata are transformed into a common scale to permit meaningful comparisonand analysis. To standardize a data set, individual values are convertedto z-scores by using the mean and standard deviation of the data set. Tonormalize a data set, the individual values are put in order, and thentransformed into a normal curve, from which a normal order statisticmedian is calculated.

The underlying data remain available for detailed analysis in order toreview the specific conditions reported for an individual runway duringa specific interval of time. However, to preserve anonymity ofindividual pilots and air carriers, the recorded braking action valuesare intentionally disassociated from any individual aircraft, pilot andlanding.

The information used in the foregoing calculations is of three types:aircraft-specific (aircraft equipment and specifications),runway-specific (altitude and slope), and environment-specific(temperature, pressure and dew point). According to the computationalmethod disclosed above, standardized or normalized braking frictioncoefficients are calculated and reported independent of individualaircraft, tire and other aircraft-specific parameters.

The computational method of the present invention, in contrast to priorart methods, takes into account relevant tire parameters and computesseveral significant aircraft-dependent dynamic forces, and is thereforeable to account for variations among aircraft and equipment. In this waythe present invention is able to produce and deliver a normalized andtherefore more meaningful braking friction and runway condition reportregardless of individual aircraft type, tire variations and runwaysurface types.

This method of measurement, calculation and reporting of standardized ornormalized braking action coefficients beneficially incorporatesredundancy at many levels. By incorporating data from two or moresuccessive landing aircraft, multiple measurements are used toredundantly calculate and report actual runway surface conditions inreal-time. As successive landings proceed on a given runway, alllandings within a specific selected time interval may be used tocalculate a weighted average, which is then reported to downstream usersas being the actual braking conditions on that runway during thatinterval of time.

As a further advantage of the invention, redundancy is also incorporatedinto the computations of the runway conditions for any single givenlanding. As the aircraft decelerates through its landing roll, data iscalculated along the entire path of the roll, and not just at certainselected points such as at touchdown and turnoff. These data points areaveraged, creating a summary report of useful coefficient of frictionvalues all along the aircraft's path along the runway, includingtouchdown, midpoint, and rollout segments. The resulting values are thenused to compute a single overall summary value for the runway as awhole.

Finally, the summary coefficient of friction values for each of asubject airport's active runways are used to compute a single weightedsummary value that accurately represents the overall condition of theairport as a whole, and is therefore of significant use to subsequentlanding aircraft and airport operations personnel as well as air trafficcontrol (ATC).

Among the advantages of continuously generating and reporting multiplesummary values is that they afford a quick and easily understoodrepresentation of the airport runway conditions at any given time. Sucha report can be read at a glance to indicate the state of each subjectairport and runway of interest. As an added benefit, the availability ofthe underlying data allows airport and air carrier managers to at alater time look deeper into the data to obtain very specific localizedrunway condition information to for optimizing runway maintenance.

Additionally, air carriers can benefit from the use of the invention byhaving detailed real-time information as to not just current landingconditions, but more importantly, developing trends at each individualairport. The resulting benefits will include improved safety from betterflight operations decisions, better pilot and crew sequencing decisions,better fuel and cargo weight management, and cost savings from reducedin-air holding patterns and optimized landing and taxiing sequences.Improvements in schedule reliability, baggage transfer and customerservice are additional benefits which can be expected.

It is additionally expected that airports employing the invention willbenefit from having a periodic, standardized and empirical measure ofboth real-time braking action conditions, and developing trends inbraking action. Particularly when operating in inclement weather, withsnow, ice, and hydroplaning conditions caused by winds and rain, airportoperators can by use of the invention optimize runway closure andmaintenance decisions.

Because of the invention's ability to record and report real-time data,at the most active commercial airports it can be expected that brakingaction reports will be generated within minutes of each other. This datapattern will thereby enable the airport managers to continuously monitorrunway conditions during periods of high activity and thus limit theneed to shut a runway down for ground-based measurement tests.Presently, without the benefits of the present invention, such groundtests can take as much as 15 to 25 minutes each, requiring ATC to placemany arriving aircraft in time-wasting and fuel-wasting holdingpatterns. At some large airports it can take 30 minutes or more to movemaintenance equipment into place and to clean a runway of snow and ice.

By employing the present invention, airport management and ATC will alsobe able to follow developing trends in the braking action on individualrunways, which will necessarily improve airport operations and flowcontrol decisions, and most of all, aviation safety in general. Airportoperations will realize cost savings, operational efficiencies andimproved customer service benefits. Air carriers will likewise realizesubstantial cost savings.

Off-Board Real-Time Processing. According to another embodiment of theinvention, the actual aircraft runway braking performance is determinedby calculating in real-time by means of off-board data processing (FIGS.8, 9, 11). In this embodiment, all monitored parameters are fedreal-time into a wired or wireless system, such as ACARS, WirelessGround Link or similar digital wireless communication system which iscapable of transmitting, with sufficient speed and bandwidth, data fromthe aircraft to a remote ground location, with time delays sufficientlysmall to be considered real-time or near real-time.

With reference to FIG. 11, the remote location receiving the data streamreal-time from the aircraft is equipped with a communication systemcapable of accepting the real-time data stream from the aircraft's FDMS11.1 and transmitting the data 11.3 real-time to an off-aircraft highpowered computer system 11.4, while also storing the data in an on-boarddate storage means 11.2. The off-aircraft high power computer system iscapable of processing the data and calculating all relevant physicalprocesses involved in the aircraft landing maneuver.

Based upon the real-time calculated physical information, the actualeffective braking friction coefficient of the landing aircraft iscalculated in the manner previously described. This information,together with other parameters and weather data, is then used tocalculate the true aircraft landing performance parameters, includingnormalized true braking coefficient of friction. The calculated trueaircraft landing performance parameters thus constitute the trueeffective braking friction coefficient, the true effective corneringfriction coefficient, and the estimated true runway conditions. Fromthis information other performance parameters can also be calculated anddistributed.

The following steps are utilized in practicing this aspect of theinvention, as best illustrated in FIG. 11:

11.1—Acquisition. All monitored and available data from the aircraft'son-board transducers and instrumentation is sent to the aircraft'sflight data management system throughout the aircraft landing and groundmaneuver.

11.2—Collection, processing and storage. The FDMS collects, processesand stores the retrieved data in a raw data storage means. The datastorage means can be, and in most modern aircraft avionics system is,part of the FDMS in which all the acquired data is stored.

11.3—Data Transfer. The stored data is taken from the data storagemeans, conditioned and sent through communication channels, for example,through satellite communication ACARS or similar system or wirelessground link system such as WGL system, to a remote ground locationreal-time or near real-time.

11.4—High power computer system. The remote location is equipped withsuitable communication equipment to receive the transmitted data inreal-time. All the transmitted parameters are recorded and fed real-timeinto a suitable high-power computer system which is capable ofprocessing the data and calculating and/or simulating all relevantphysical processes involved in the aircraft landing maneuver, andthereby determining the actual effective braking friction coefficient ofthe landing aircraft, and the true aircraft landing performanceparameters.

11.5—Distribution. The high-power computer system in the remote locationis then utilized to distribute the calculated true aircraft runwaylanding parameters to other interested parties through wired, wireless,internet, mobile phone, fax, email or other communication channels.

I claim:
 1. A computer network for calculating and distributing a trueaircraft braking friction coefficient for an aircraft runway or taxiwaycomprising: (A) An aircraft having a flight data management system forrecording one or more sets of data points thereon, wherein the one ormore sets of data points pertain to one or more of the followingaircraft properties measured at various times for the aircraft: aircraftground speed, aircraft brake pressure, aircraft longitudinalacceleration, aircraft engine thrust setting, aircraft reverse thrustsetting, aircraft engine revolutions per minute, aircraft air speed,aircraft vertical acceleration, aircraft spoiler setting, aircraftairbrake setting, aircraft aileron setting, aircraft flap configuration,aircraft pitch, and aircraft autobrake setting; (B) A computer incommunication with the flight data management system of the aircraftwhich obtains from the aircraft's flight data management system the oneor more sets of data points pertaining to the one or more aircraftproperties; and (C) Wherein the computer calculates the true aircraftbraking friction coefficient of the aircraft runway or taxiway using atleast one of the one or more sets of the data points obtained from theaircraft's flight data management system by the computer.
 2. Thecomputer network for calculating and distributing the true aircraftbraking friction coefficient of the aircraft runway or taxiway of claim1 wherein the aircraft's flight data management system further comprisesa flight data recorder.
 3. The computer network for calculating anddistributing the true aircraft braking friction coefficient of theaircraft runway or taxiway of claim 1 wherein the aircraft's flight datamanagement system further comprises a quick access recorder.
 4. Thecomputer network for calculating and distributing the true aircraftbraking friction coefficient of the aircraft runway or taxiway of claim1 wherein the computer is located on the aircraft.
 5. The computernetwork for calculating and distributing the true aircraft brakingfriction coefficient of the aircraft runway or taxiway of claim 2wherein the computer is located on the aircraft.
 6. The computer networkfor calculating and distributing the true aircraft braking frictioncoefficient of the aircraft runway or taxiway of claim 3 wherein thecomputer is located on the aircraft.
 7. The computer network forcalculating and distributing the true aircraft braking frictioncoefficient of the aircraft runway or taxiway of claim 1: (A) Whereinthe computer communicates with one or more sources of one or more setsof data points pertaining to one or more environmental parametersmeasured substantially in the vicinity of the aircraft, and wherein theone or more sets of data points relating to the one or moreenvironmental parameters relate to one or more environmental parameterschosen from the following group: air temperature, air pressure, relativehumidity, wind speed, wind direction, pressure altitude, and aircraftsurface elevation; (B) Wherein the computer obtains the one or more setsof data points pertaining to the one or more environmental parameters;and (C) Wherein the computer calculates the true aircraft brakingfriction coefficient of the aircraft runway or taxiway using at leastone of the one or more of sets of data points pertaining to the one ormore environmental parameters.
 8. The computer network for calculatingand distributing the true aircraft braking friction coefficient of theaircraft runway or taxiway of claim 4: (A) Wherein the computercommunicates with one or more sources of one or more sets of data pointspertaining to one or more environmental parameters measuredsubstantially in the vicinity of the aircraft, and wherein the one ormore sets of data points relating to the one or more environmentalparameters relate to one or more environmental parameters chosen fromthe following group: air temperature, air pressure, relative humidity,wind speed, wind direction, pressure altitude, and aircraft surfaceelevation; (B) Wherein the computer obtains the one or more sets of datapoints pertaining to the one or more environmental parameters; and (C)Wherein the computer calculates the true aircraft braking frictioncoefficient of the aircraft runway or taxiway using at least one of theone or more of sets of data points pertaining to the one or moreenvironmental parameters.
 9. The computer network for calculating anddistributing the true aircraft braking friction coefficient of theaircraft runway or taxiway of claim 1: (A) Wherein the computercommunicates with one or more sources of one or more sets of data pointsrelating to aircraft parameters pertaining to the aircraft, and whereinthe one or more sets of data points relating to the one or more aircraftparameters relate to one or more aircraft parameters chosen from thefollowing group: aircraft landing mass, aircraft engine type, number ofaircraft engines, aircraft tire type, and aircraft type; (B) Wherein thecomputer obtains the one or more sets of data points pertaining to theone or more aircraft parameters; and (C) Wherein the computer calculatesthe true aircraft braking friction coefficient of the aircraft runway ortaxiway using at least one of the one or more of sets of data pointspertaining to the one or more aircraft parameters.
 10. The computernetwork for calculating and distributing the true aircraft brakingfriction coefficient of the aircraft runway or taxiway of claim 4: (A)Wherein the computer communicates with one or more sources of one ormore sets of data points relating to aircraft parameters pertaining tothe aircraft, and wherein the one or more sets of data points relatingto the one or more aircraft parameters relate to one or more aircraftparameters chosen from the following group: aircraft landing mass,aircraft engine type, number of aircraft engines, aircraft tire type,and aircraft type; (B) Wherein the computer obtains the one or more setsof data points pertaining to the one or more aircraft parameters; and(C) Wherein the computer calculates the true aircraft braking frictioncoefficient of the aircraft runway or taxiway using at least one of theone or more of sets of data points pertaining to the one or moreaircraft parameters.
 11. The computer network for calculating anddistributing the true aircraft braking friction coefficient of theaircraft runway or taxiway of claim 7: (A) Wherein the computercommunicates with one or more sources of one or more sets of data pointsrelating to aircraft parameters pertaining to the aircraft, and whereinthe one or more sets of data points relating to the one or more aircraftparameters relate to one or more aircraft parameters chosen from thefollowing group: aircraft landing mass, aircraft engine type, number ofaircraft engines, aircraft tire type, and aircraft type; (B) Wherein thecomputer obtains the one or more sets of data points pertaining to theone or more aircraft parameters; and (C) Wherein the computer calculatesthe true aircraft braking friction coefficient of the aircraft runway ortaxiway using at least one of the one or more of sets of data pointspertaining to the one or more aircraft parameters.
 12. The computernetwork for calculating and distributing the true aircraft brakingfriction coefficient of the aircraft runway or taxiway of claim 8: (A)Wherein the computer communicates with one or more sources of one ormore data points relating to aircraft parameters pertaining to theaircraft, and wherein the one or more sets of the data points relatingto the one or more aircraft parameters relate to one or more aircraftparameters chosen from the following group: aircraft landing mass,aircraft engine type, number of aircraft engines, aircraft tire type,and aircraft type; (B) Wherein the computer obtains the one or more setsof data points pertaining to the one or more aircraft parameters fromthe one or more sources of data points pertaining to the one or moreaircraft parameters; and (C) Wherein the computer calculates the trueaircraft braking friction coefficient of the aircraft runway or taxiwayusing at least one of the one or more of sets of data points obtainedfrom the one or more sources of data points pertaining to the one ormore aircraft parameters.
 13. The computer network for calculating anddistributing the true aircraft braking friction coefficient of theaircraft runway or taxiway of claim 1, wherein the computer communicateswith and distributes the true aircraft braking friction coefficient toone or more individuals or entities chosen from the following: airlineoperation personnel, pilots, airport personnel, airline managers,airport managers, airport maintenance crews, pilots of aircraftscheduled to take off, land, or taxi on the aircraft runway or taxiway,personnel involved in ground operations where the aircraft runway ortaxiway is located, aircraft scheduling and dispatch personnel, flightservice center personnel, government aviation authority personnel, airtraffic controllers, airline employees, and aircraft manufacturers. 14.A computer network for calculating and distributing a normalized trueaircraft braking friction coefficient for an aircraft runway or taxiwaycomprising: (A) A first aircraft having a first flight data managementsystem for recording one or more sets of data points thereon, whereinthe one or more sets of data points pertain to one or more of thefollowing first aircraft properties measured at various times for thefirst aircraft: aircraft ground speed, aircraft brake pressure, aircraftlongitudinal acceleration, aircraft engine thrust setting, aircraftreverse thrust setting, aircraft engine revolutions per minute, aircraftair speed, aircraft vertical acceleration, aircraft spoiler setting,aircraft airbrake setting, aircraft aileron setting, aircraft flapconfiguration, aircraft pitch, and aircraft autobrake setting; (B) Acomputer in communication with the first flight data management systemof the first aircraft which obtains from the first aircraft's firstflight data management system the one or more sets of data pointspertaining to the one or more first aircraft properties; (C) Wherein thecomputer calculates the first true aircraft braking friction coefficientof the aircraft runway or taxiway using at least one of the one or moreof sets of the data points obtained from the first aircraft's firstflight data management system by the computer; (D) A second aircrafthaving a second flight data management system for recording one or moresets of data points thereon, wherein the one or more sets of data pointspertain to one or more of the following second aircraft propertiesmeasured at various times for the second aircraft: aircraft groundspeed, aircraft brake pressure, aircraft longitudinal acceleration,aircraft engine thrust setting, aircraft reverse thrust setting,aircraft engine revolutions per minute, aircraft air speed, aircraftvertical acceleration, aircraft spoiler setting, aircraft airbrakesetting, aircraft aileron setting, aircraft flap configuration, aircraftpitch, and aircraft autobrake setting; (E) A computer in communicationwith the second flight data management system of the second aircraftwhich obtains from the second aircraft's second flight data managementsystem the one or more sets of data points pertaining to the one or moresecond aircraft properties; (F) Wherein the computer calculates thesecond true aircraft braking friction coefficient of the aircraft runwayor taxiway using at least one of the one or more of the sets of the datapoints obtained from the second aircraft's second flight data managementsystem by the computer; and (G) Wherein the computer uses the first andsecond true aircraft braking friction coefficients of the aircraftrunway or taxiway to calculate a normalized aircraft braking frictioncoefficient of the aircraft runway or taxiway.
 15. The computer networkfor calculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 14,wherein the computer communicates with and distributes the normalizedtrue aircraft braking friction coefficient to one or more individuals orentities chosen from the following: airline operation personnel, pilots,airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 16. The computer networkfor calculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 14: (A)Wherein the computer communicates with one or more sources of one ormore sets of data points pertaining to one or more environmentalparameters measured substantially in the vicinity of the first aircraft,and wherein the one or more sets of data points relating to the one ormore environmental parameters relate to one or more environmentalparameters chosen from the following group: air temperature, airpressure, relative humidity, wind speed, wind direction, pressurealtitude, and aircraft surface elevation; (B) Wherein the computerobtains the one or more sets of data points pertaining to the one ormore environmental parameters measured substantially in the vicinity ofthe first aircraft; and (C) Wherein the computer calculates thenormalized true aircraft braking friction coefficient of the aircraftrunway or taxiway using at least one of the one or more of sets of datapoints pertaining to the one or more environmental parameters measuredin the vicinity of the first aircraft.
 17. The computer network forcalculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 14: (A)Wherein the computer communicates with one or more sources of one ormore sets of data points relating to first aircraft parameterspertaining to the first aircraft, and wherein the one or more sets ofdata points relating to the one or more first aircraft parameters relateto one or more aircraft parameters chosen from the following group:aircraft landing mass, aircraft engine type, number of aircraft engines,aircraft tire type, and aircraft type; (B) Wherein the computer obtainsthe one or more sets of data points pertaining to the one or more firstaircraft parameters; (C) Wherein the computer calculates the first trueaircraft braking friction coefficient of the aircraft runway or taxiwayusing at least one of the one or more of sets of data points pertainingto the one or more first aircraft parameters; (D) Wherein the computercommunicates with one or more sources of one or more sets of data pointsrelating to second aircraft parameters pertaining to the secondaircraft, and wherein the one or more sets of data points relating tothe one or more second aircraft parameters relate to one or moreaircraft parameters chosen from the following group: aircraft landingmass, aircraft engine type, number of aircraft engines, aircraft tiretype, and aircraft type; (E) Wherein the computer obtains the one ormore sets of data points pertaining to the one or more second aircraftparameters; and (F) Wherein the computer calculates the second trueaircraft braking friction coefficient of the aircraft runway or taxiwayusing at least one of the one or more of sets of data points pertainingto the one or more second aircraft parameters.
 18. The computer networkfor calculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 16: (A)Wherein the computer communicates with one or more sources of one ormore sets of data points relating to first aircraft parameterspertaining to the first aircraft, and wherein the one or more sets ofdata points relating to the one or more first aircraft parameters relateto one or more aircraft parameters chosen from the following group:aircraft landing mass, aircraft engine type, number of aircraft engines,aircraft tire type, and aircraft type; (B) Wherein the computer obtainsthe one or more sets of data points pertaining to the one or more firstaircraft parameters; (C) Wherein the computer calculates the first trueaircraft braking friction coefficient of the aircraft runway or taxiwayusing at least one of the one or more of sets of data points pertainingto the one or more first aircraft parameters; (D) Wherein the computercommunicates with one or more sources of one or more sets of data pointsrelating to second aircraft parameters pertaining to the secondaircraft, and wherein the one or more sets of data points relating tothe one or more second aircraft parameters relate to one or moreaircraft parameters chosen from the following group: aircraft landingmass, aircraft engine type, number of aircraft engines, aircraft tiretype, and aircraft type; (E) Wherein the computer obtains the one ormore sets of data points pertaining to the one or more second aircraftparameters; and (F) Wherein the computer calculates the second trueaircraft braking friction coefficient of the aircraft runway or taxiwayusing at least one of the one or more of sets of data points pertainingto the one or more second aircraft parameters.
 19. The computer networkfor calculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 16,wherein the computer communicates with and distributes the normalizedtrue aircraft braking friction coefficient to one or more individuals orentities chosen from the following: airline operation personnel, pilots,airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 20. The computer networkfor calculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 18,wherein the computer communicates with and distributes the normalizedtrue aircraft braking friction coefficient to one or more individuals orentities chosen from the following: airline operation personnel, pilots,airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 21. The computer networkfor calculating and distributing the true aircraft braking frictioncoefficient for an aircraft runway or taxiway of claim 13 wherein thecomputer is located on the aircraft.
 22. The computer network forcalculating and distributing the normalized true aircraft brakingfriction coefficient for the aircraft runway or taxiway of claim 14wherein the computer is located on the aircraft.
 23. The computernetwork for calculating and distributing the normalized true aircraftbraking friction coefficient for the aircraft runway or taxiway of claim15 wherein the computer is located on the aircraft.
 24. The computernetwork for calculating and distributing the normalized true aircraftbraking friction coefficient for the aircraft runway or taxiway of claim16 wherein the computer is located on the aircraft.
 25. The computernetwork for calculating and distributing the normalized true aircraftbraking friction coefficient for the aircraft runway or taxiway of claim17 wherein the computer is located on the aircraft.
 26. The computernetwork for calculating and distributing the normalized true aircraftbraking friction coefficient for the aircraft runway or taxiway of claim18 wherein the computer is located on the aircraft.
 27. The computernetwork for calculating and distributing the normalized true aircraftbraking friction coefficient for the aircraft runway or taxiway of claim19 wherein the computer is located on the aircraft.
 28. The computernetwork for calculating and distributing the normalized true aircraftbraking friction coefficient for the aircraft runway or taxiway of claim20 wherein the computer is located on the aircraft.